1. Field of the Invention
This invention relates to an image processing apparatus and method as well as an image forming system, apparatus and method. More particularly, the invention relates to an image processing apparatus and method as well as an image forming system, apparatus and method having a function for developing image data described in page description language, by way of example.
2. Description of the Related Art
When a printing job extending over several pages is to be handled by a printer having a PDL (page description language) controller for developing image data described in PDL, the raster image data for all of the pages cannot always be stored in a frame memory that is for the purpose of storing the raster image data after development. Accordingly, while one page is being printed, the printer develops the PDL data for subsequent pages. The time required to develop PDL data depends upon the content of the image; the more complicated the image, the longer the time required. This means that if the development of the PDL data is not finished by the time the printing of the preceding page ends, the printer engine is halted temporarily and restarted once the development of the PDL data has been completed.
When the printer engine is temporarily halted, a transition is made to a stopping operation referred to as xe2x80x9cbackward rotationxe2x80x9d. Then, when printing is started again, a transition is made to a starting operation referred to as xe2x80x9cforward rotationxe2x80x9d and to a paper-feed operation. Consequently, even if printing is restarted immediately after the temporary halting of the printer engine, total printing time is much longer than it would be for a continuous printing operation. This results in a conspicuous decline in performance in a case where a copier having a long paper path from the cassette to the transfer drum and fixing unit is used as the printer.
Since a frame memory for raster images is high in cost, a frame memory capable of storing a large number of pages at one time is not provided. In addition, the time required for developing PDL data is longer than that required for printing. For these reasons, many printers always halt the operation of the printer engine between pages. Alternatively, a method is adopted in which the printer engine initially is instructed to perform a printing job consisting of a sufficiently large number of pages and the printer engine is halted temporarily if the development of the PDL data fails to keep pace.
The recent decline in the cost of DRAMs of larger storage capacity has been accompanied by the potential for frame memories capable of storing a large number of pages. In addition, the time needed to develop PDL data is being made shorter by high-speed CPUs of RISC type. With this as a background, it is hoped that total printing time will be shortened by executing continuous printing achieved by halting the printer engine as little as possible.
However, the following problem arises in the art described above:
With the method of instructing the printer engine to perform a printing job consisting of a sufficiently large number of pages, the PDL controller must judge whether the printer engine is to be stopped or not. As a consequence, control becomes extremely complicated in a case where the paper-feed cassettes are arranged in three or four stages and the timing at which paper feed starts is different for each cassette stage, or in a case where the paper is fed in advance to color image developed by a printer controller. Further, if the printer-engine stop command is not issued by the PDL controller for some reason, the printer engine will output blank paper.
Accordingly, an object of the present invention is to provide an image forming apparatus, as well as a controller for the same, in which total printing time can be shortened by simple control.
Another object of the present invention is to provide an image forming apparatus, as well as a controller for the same, in which even if a printer engine for performing advance feed of paper is made to perform a printing job, total printing time can be shortened by simple control.
A further object of the present invention is to provide an image forming apparatus, as well as a controller for the same, in which the output of a recording medium, fed in advance, without the formation of an image thereon is prevented by simple control.
According to the present invention, an image forming apparatus of a preferred embodiment that attains the foregoing object comprises generating means for successively generating at least one page of image data from entered image information and outputting the number of copies of images formed based upon these image data, first counting means for successively counting the number of image data generated by the generating means and for outputting a first count value, image storage means for storing at least one page of the image data generated by the generating means, formed-copy count storage means for storing the number of formed copies outputted by the generating means, forming means for forming images, the number of which is the number of formed copies stored in the formed-copy count storage means, on a supplied recording medium based upon the image data stored in the image storage means, second counting means for counting the number of recording media that have been supplied to the forming means and outputting a second count value, and control means comparing the first count value and the second count value at a predetermined timing and controlling the supply of the recording medium to the forming means in dependence upon results of the comparison.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.